In oil and other hydrocarbon production operations, completion, drilling and workover fluids are typically circulated down the string of tubes and upwards around the outside of the tubes, contacting the formation surface of the wellbore from which the hydrocarbons are to be produced. Part of the fluid may be lost into the formation, and frequently the fluid is diluted by indigenous fluid entering from the formation. The salts and other additives in the completion or workover fluid are either partially lost or diluted, or both, as a result of contact with the formation. It is desirable in many instances to use additives which contribute a degree of density to the completion or workover fluid; that is, a dense brine will be able more efficiently to remove loose rock and sand, for example, which otherwise might clog the perforations in the pipe, thus impeding hydrocarbon production. As a relatively heavy alkali metal, cesium works well as a densifying agent in completion and workover fluids, but it is expensive, and, as with any other material which must ultimately be disposed of, should be recycled to the extent reasonably possible. This invention is directed specifically to the recycling of cesium as a densifying agent in completion, drilling and workover fluids and to similar treatment of solutions of cesium obtained in the mining of cesium.
As used herein, the term “heavy brine components” means calcium, zinc, ammonium and/or cesium as cations and chloride, formate and particularly bromide as anions from any source. Typical sources include cesium chloride or formate, calcium chloride, sodium chloride, sodium bromide, calcium bromide, zinc chloride, zinc bromide, ammonium chloride, and mixtures thereof as well as their cation and anion forming moieties from other sources.
Many oil well fluids contain polymers added for various purposes including to increase viscosity to help remove solids from the well and to retard the fluid loss into the formation. Polymers may be considered contaminants for various types of recycling, and in any event are difficult to remove, particularly when they are present with substantial quantities of solids.
Oil well muds generally include large proportions of solids, making their disposal difficult; also they contain additives which are beneficially recovered and recycled. Disposal is also difficult for other common oil well fluids such as water/oil (or oil/water) emulsions of widely varying composition including muds; recovering the more valuable components of emulsions for recycling or other use has been very difficult.
Not least among the difficulties of dealing with dilute, spent or used oil well fluids is the mundane but expensive task of trucking the fluids from remote producing wells to distant environmentally approved disposal sites or processing plants. Quite apart from the utter waste of materials, the cost of hauling dilute brines and other oil well fluids for disposal is a serious counterproductive burden to the producer. A related point is that if the excess water in dilute fluids is not eliminated or recovered for various purposes, the volume of fluid at the wellsite continues to increase, requiring more and more additives to render it useful. Such additions are costly, as are the facilities necessary to store the additional fluid.
As our invention is capable of concentrating and remediating any or all of the above described oil well fluids—brines, heavy brines, polymer-containing fluids, completion and workover fluids, drilling fluids, muds, and emulsions—we may refer to these collectively herein as “oil well fluids.” Similar fluids are used in the production of natural gas in gas wells, and accordingly we intend to include such fluids in the term oil well fluids. Oil well fluids generally may include high solids contents, but muds in particular may include solids commonly in the range of up to about 45% by volume. Such high solids content is detrimental to any conventional distillation process which might be considered to treat an oil field mud for recycling. Likewise emulsions are not conducive to conventional distillation as a separate procedure. Conventional distillation methods of concentrating dilute and particularly contaminated solutions including heavy brine components result in scaling and other difficulties which ultimately frustrate the economics of recycling. A more economical method is needed for recycling the components of oil well fluids.
Common alkali metal salts such as sodium or potassium chloride, bromide or formate have long been used in oil well completion, drilling and workover fluids (collectively herein called oil well fluids). The more unusual cesium salts have been found particularly useful where a denser fluid is needed. Conventional distillation methods of concentrating dilute and particularly contaminated solutions of cesium salts result in scaling and other difficulties which ultimately frustrate the economics of recycling.
Because of the particular difficulties of handling and dewatering cesium solutions, and because of their expense and the unique environmental aspects of cesium, this application is directed specifically to the concentration of cesium solutions and recycling where appropriate. A more economical method of recycling cesium is needed for oil well fluids.